Endangered Species Handbook

Print PDF of Section or Chapter

Aquatic Ecosystems

Destruction of Aquatic Ecosystems

     As aquatic habitats are destroyed bit by bit, countless creatures and plants disappear.  Crystalline bodies of water that furnished ample water to wildlife and people alike only a few centuries ago have become polluted or dried up. Growing human populations and development consume millions of acres of ecologically important coastal marshes and mangrove swamps to make way for airports, urban development, seaports, shrimp farms and resorts.  More subtle changes are occurring from ozone depletion, acid rain and global warming caused by chemical pollutants in the atmosphere.  These may end in far-reaching ecological changes and extinctions that are only beginning to be chronicled. 
 
     Less than 3 percent of the Earth's water is fresh, and two-thirds of it is frozen in glaciers and ice caps.  The remaining 0.5 percent is contained in aquifers, rivers, marshes, other wetlands and in the atmosphere (Barlow 1999).   Global population growth is expected to outpace freshwater supplies by 56 percent by 2025 unless patterns of use change radically (Barlow 1999).  Water use has grown at more than twice the rate of population increase in the 20th century, according to the United Nations (Barlow 1999).  Almost 70 percent of the world's population lives in areas bordering bodies of water such as rivers, coastlines and lakes, where civilizations have traditionally arisen (Dugan 1993).  The United Nations reports some 80 countries, 40 percent of the world's population, are already facing water shortages (Lewis 1996).  At least 20 percent of the world's peoples do not have clean water for drinking, according to a 1997 conference of Earth Summit Plus (Grossfeld 1997).  Cities have been increasing in size, and the United Nations predicts that within a decade, most of the world's peoples will live in cities for the first time in the human history.  Currently, 2.6 billion people live in urban areas; this total is expected to rise to 3.3 billion by 2005 (Lynch 1996).  By 2025, 5 billion people, or almost all people now living on Earth, are expected to be city-dwellers, the vast majority in poor countries without effective pollution control or sufficient water supply, by UN estimates.
 
     The United Nations believes that by 2025, the world's population will number 8.3 billion, with two-thirds living in conditions of serious water shortage and one-third suffering from severe water scarcity (Barlow 1999).  Growing urban populations require more and more fresh water.  Rivers and lakes have been dammed, diverted and channeled to supply these cities, often with disastrous consequences for wildlife.  Since all portions of a river are part of the same ecosystem, when it is dammed or altered, the river and its wildlife and plants are affected throughout its length, which may extend over 1,000 miles.  Wetlands at the mouth of a river can be drained by the construction of a dam hundreds of miles inland.  Likewise, channeling at the mouth of a river, increasing flow for ship navigation, can drain wetlands and alter flow for the entire length of the river, eliminating native wildlife and plants.  The Missouri River, for example, was once a shallow, sandy-bottomed river lined with trees and swamps.  When Lewis and Clark explored the region in the early 19th century, they saw great numbers of sturgeon, trout and other fish, aquatic mammals, and vast flocks of cranes, waterfowl and shorebirds.  During the 20th century, multiple dams were built, and the river was channeled to accommodate ship traffic, radically altering the Missouri's ecosystem.  The shallow-water feeding grounds for birds were drowned, and migratory sturgeon and trout found their routes blocked, endangering many species.  After much opposition from barge operators and farmers, Congress funded a program in October 2000 to partially restore the flow to accommodate the needs of native wildlife by altering water releases from dams for a few months each year.  Many conservationists are working to save even more of this original ecosystem.
 
     Underground aquifers contain water that has been accumulating for thousands of yearsOnly in recent decades have they been exploited, and many are being over-pumped for city water supplies or agriculture.   The High Plains Ogallala aquifer in the Great Plains of the United States stretches from South Dakota to Texas; pumping is depleting it eight times faster than it can be replenished naturally (Barlow 1999).  This story is being repeated around the world, especially in desert regions such as North Africa, northern China and the Saudi Arabian peninsula, where fossil aquifers are being over-pumped for agriculture, industry and household use (Barlow 1999).  This is resulting in their gradual depletion, contributing to a future "water bankruptcy" (Barlow 1999).  Countries in arid regions are already competing for scarce water supplies.  The Euphrates River has been dammed by Turkey, turning its flow to a trickle by the time it reaches Iraq.  The latter country has become increasingly arid over the past few thousand years as grassland and bountiful water supplies deteriorated to desert as a result of over-use of water and drainage of wetlands.  
 
     Trade treaties, such as the North American Free Trade Agreement (NAFTA) signed between the United States, Canada and Mexico and the World Trade Organization (WTO), whose members include the majority of countries, override national water rights, assigning them to corporations and other commercial interests.  Water is now being bought and sold as a commodity.  One large company, the US Global Water Corporation, has signed an agreement with Sitka, Alaska, to transport 18 billion gallons of glacier water per year to China, where it will be bottled and sold (Barlow 1999).  A California company was denied the ability to purchase water from British Columbia and, under the principles of NAFTA, sued the government of Canada for $220 million (Barlow 1999). Environmental and species preservation are not considered in these global transactions.  By treating water as a commodity to be traded to the highest bidder, ecosystems will be devastated.  The International Forum on Globalization of San Francisco outlines many of these issues that point toward future catastrophes for the environment and human society alike in its report, Blue Gold.  It concludes that only if water is considered to be commonly shared by humans and all species, and water diversion, damming, pollution, sale and bartering are halted, can there be hope for the future (Barlow 1999).
 
     In the United States, only the onset of droughts brings about restrictions on water usage.  Agriculture and livestock use an estimated 65 percent of the country's water supplies, households 10 percent and industry 25 percent.  Much of the water used for agriculture comes from diverted rivers in irrigation programs which return it to water tables contaminated with large amounts of pesticides, herbicides and artificial fertilizers.  An American family of four uses 300 gallons a day, far more than the average in most of the rest of the world.  This profligacy has been at the expense of natural ecosystems.  As human populations grow, water use will result in ever more strain on water supplies.  Cities have sprung up in near-desert regions in the United States, requiring water diversion from other areas.  One of the most dramatic examples of this is Los Angeles.  The major flows from several rivers and lakes have been diverted to supply the needs of Los Angeles (Reisner 1986). Only with artificial water supplies has this city been able to grow to metropolis size.  Its denizens waste their water supply to grow green lawns, and an enormous amount is used by local industry and agriculture. Los Angeles' water has been supplied at the expense of wildlife and plant species native to the diverted and drained water bodies, many of which are now endangered (Reisner 1986).  Salmon and other fish have become endangered in the source rivers and lakes used to supply Los Angeles.  Las Vegas, Phoenix and other western cities also tap the scarce water resources of the West. The diversion of water from natural rivers and lakes for large cities and massive agriculture projects is destroying aquatic oases in dry areas and drying up entire rivers in deserts, endangering species as diverse as tortoises, Bald Eagles (Haliaeetus leucocephalus) and songbirds.
 
      Half of the people in developing countries suffer from illnesses associated with contaminated water, such as chronic diarrhea (Grossfeld 1997), and more than 5 million people, most of them children, die every year from these illnesses (Barlow 1999).  Conflicts over water resources between countries and states are increasing, and in the future, wars may be fought over dwindling water supplies.
 
      Although marshes are able to filter limited amounts of nutrient-laden water, raw, untreated sewage dumped into waterways can turn them into fetid, oxygenless mires.  Ninety percent of the sewage in the swelling cities of poor countries is untreated, having had none of the solid matter removed, according to the World Resources Institute in Washington, DC.  Some rivers, such as the Ganges and Brahmaputra River systems, are so polluted that the native dolphin, the endangered Ganges River Dolphin (Platanista gangetica), struggles to survive in the contaminated water.  Fish are killed by the pollution, leaving the dolphins without food, and the high bacteria counts may be killing these dolphins directly.  The Ganges has become so sewage-laden that it presents major health risks to the people who drink from and bathe in its water.  This is especially ironic because this river is a holy river to the millions of Hindus who come to anoint themselves in its water.   India has more than 3,000 towns and cities, but only eight of these have sewage treatment plants (Crossette 1996).  Even sewage treatment systems can overflow during heavy rains, spilling toxic chemicals and oily runoff from roads, as well as untreated sewage.  Since almost half of the world's population lives in cities, this is one of the world's most serious environmental problems.
 
     The failure to conserve forests and vegetation has become a major factor in destroying natural aquatic ecosystems around the world.  Besides causing mud slides and floods, the cutting of trees bordering rivers and streams also results in a rise in water temperature that affects the local climate and kills fish eggs and other wildlife.  Clear-cut logging also causes siltation of rivers and lakes, smothering fish and wildlife.  Salamanders, who require damp, undisturbed forest floors, are often eliminated by clear-cut logging.  James Petranka of the University of North Carolina estimates that in the national forests of North Carolina, 14 million salamanders are wiped out every year by clear-cutting (Stolzenburg 1997). Extreme deforestation causes streams, springs, ponds and rivers to dry up and the regional climate to become more arid. 
      
     Oceans were once thought resilient to heavy pollution and the dumping of all types of debris.  We are learning, however, that the combined effects of overfishing, killing of coral reefs and toxic contamination are turning them into aquatic deserts, according to Dr. Sylvia Earle, an eminent oceanographic scientist, and conservationist-author, Carl Safina (Earle and Henry 1999, Safina 1997).  The oceans have also become crowded with commercial ships, fishing boats and pleasure craft, all of which are causing problems for wildlife.  These ships discard plastics and other material and pose a threat of collision.  Several cruise lines have been indicted and fined in recent years for dumping illegal materials overboard, including plastics, large amounts of waste oil and other toxic substances. 
 
      Coral reefs have proven very delicate and vulnerable to die-offs.  Pollution, overfishing, cyanide poisoning and dynamiting to obtain tropical fish for the aquarium and Asian restaurant trades, or corals for the curio trade have all contributed to severe losses in the 70 million square miles of coral reef around the world.  
 
    Natural, unpolluted aquatic environments are fast disappearing around the world.  Approximately 50 percent of the world's wetlands have been lost in historic times, according to Wetlands in Danger: A World Conservation Atlas (Dugan 1993).  In the past, wetlands were destroyed primarily for agricultural development.  Although this remains a major threat, programs such as dam construction and irrigation projects financed by the World Bank and the International Monetary Fund are becoming the major threat to pristine aquatic environments around the world.  Unfortunately, the effects of these losses are usually appreciated too late, when species disappear and water ecologies are damaged.
 
     Soils in many dryland areas have become polluted by salinization caused by irrigation schemes.  Irrigation water flowing onto drylands brings to the surface substratum minerals and salts, which render the soil unfit for agriculture or almost any natural vegetation.  Regions covering at least 150,000 square miles worldwide have become too saline to farm after irrigation programs (Dugan 1993). 


Back
Chapters
Chapter Index
Search
Animal Welfare Institute
Next
    ©1983 Animal Welfare Institute